초록
<P><B>ABSTRACT</B><P> Acetoin reductase (ACR) catalyzes the conversion of acetoin to 2,3-butanediol. Under certain conditions, Clostridium acetobutylicum ATCC 824 (and strains derived from it) generates both d - and l -stereoisomers of acetoin, but because of the absence of an ACR enzyme, it does not produce 2,3-butanediol. A gene encoding ACR from Clostridium beijerinckii NCIMB 8052 was functionally expressed in C. acetobutylicum under the control of two strong promoters, the constitutive <I>thl</I> promoter and the late exponential <I>adc</I> promoter. Both ACR-overproducing strains were grown in batch cultures, during which 89 to 90% of the natively produced acetoin was converted to 20 to 22 mM d -2,3-butanediol. The addition of a racemic mixture of acetoin led to the production of both d -2,3-butanediol and <I>meso</I> -2,3-butanediol. A metabolic network that is in agreement with the experimental data is proposed. Native 2,3-butanediol production is a first step toward a potential homofermentative 2-butanol-producing strain of C. acetobutylicum . </P></P>